Fred Reines and Clyde Cowan built the first prototype neutrino detector at one of the nuclear reactors at the Hanford Engineering Works in Washington state. This was Project Poltergeist. But they soon realized that they recorded the same average number of events even when the reactors were shut down. They therefore built a second one 12 meters underground at the Savannah River reactor, just 10 meters from the reactor core. And they finally found the elusive neutrino.
